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IRS.gov Website
Rev. date: 11/01/2012


401(k) Plans

Tax Topic 424
rule
A 401(k) plan is a qualified deferred compensation plan in which an employee can elect to have the employer contribute a portion of his or her cash wages to the plan on a pretax basis. Generally, these deferred wages (commonly referred to as elective contributions) are not subject to income tax withholding at the time of deferral, and they are not reflected on your Form 1040 since they were not included in the taxable wages on your Form W-2. However, they are included as wages subject to withholding for social security and Medicare taxes. In addition, employers must report the elective contributions as wages subject to federal unemployment taxes.
The amount that an employee may elect to defer to a 401(k) plan is limited by the Internal Revenue Code. In addition, your elective contributions may be limited based on the terms of your 401(k) plan. Refer to Publication 525, Taxable and Nontaxable Income, for more information about elective contributions. Employers should refer to Publication 560, Retirement Plans for Small Business (SEP, SIMPLE, and Qualified Plans), for information about setting up and maintaining retirement plans for employees, including 401(k) plans.
Distributions from a 401(k) plan may qualify for optional lump-sum distribution treatment or rollover treatment as long as they meet the respective requirements. For more information, refer to Tax Topic 412, Lump-Sum Distributions, and Tax Topic 413, Rollovers from Retirement Plans.
Many 401(k) plans allow employees to make a hardship withdrawal because of immediate and heavy financial needs. Generally, hardship distributions from a 401(k) plan are limited to the amount of the employees' elective contributions only, and do not include any income earned on the deferred amounts. Hardship distributions are not treated as eligible rollover distributions.
Distributions received before age 59½ are subject to an early distribution penalty of 10% additional tax unless an exception applies. For more information about the treatment of retirement plan distributions, refer to Publication 575, Pension and Annuity Income.